Technical Field
The present invention relates to an apparatus for detecting temperatures of semiconductor elements for power conversion.
Related Art
Conventionally, a known power converter, as disclosed in Japanese Patent Application Laid-Open Publication No. 2008-206345, includes a plurality of switching elements, such as insulated gate bipolar transistors (IGBTs), is configured such that temperatures of some of the plurality of switching elements can be detected by temperature sensing elements. More specifically, in such a power converter, a prespecified one of the switching elements is assumed to be hottest among the switching elements during use. In such a power converter, the plurality of switching elements are de-energized, when the detected temperature of the prespecified switching element has reached a predetermined threshold temperature. Such a power converter is thus intended to protect the switching elements from overheating.
Such a configuration that temperatures of some of the plurality of switching elements are detected may give rise to the following disadvantages.
Even though the prespecified one of the switching elements is assumed at the time of designing to be hottest during use, another switching element may actually be hottest among the switching elements during use due to aging or the like of the power converter. There is a disadvantage that, if the power converter is not configured to detect a temperature of such another switching element, all the switching elements couldn't be reliably protected from overheating based on the detected temperature of the prespecified one of the switching elements assumed at the time of designing to be hottest during use.
In addition, the temperatures of the respective switching elements may vary during flowing of collector currents through the respective switching elements due to their aging or individual difference. Therefore, when the power converter is configured to detect temperatures of some of the switching elements, the threshold temperature that is used to protect the switching elements from overheating needs to be set lower than an upper limit by a large margin for safety, below which upper limit the reliability of the switching elements can be retained. However, in such a configuration, there is a disadvantage that the overheat protecting process may be performed even though the actual temperatures of the switching elements have not yet reached the upper-limit temperature, and a temperature range where use of the switching elements is restricted may enlarge.
Power-conversion semiconductor elements, whether switching elements or not, may suffer from such disadvantages.
In consideration of the foregoing, exemplary embodiments of the present invention are directed to providing an apparatus for detecting temperatures of a plurality of semiconductor elements for power conversion, capable of preventing the semiconductor elements from overheating and preventing enlargement of a temperature range where use is restricted.